1. Technical Field
The present invention generally relates to communications networks and in particular to transmission of data packets in communications networks.
2. Description of the Related Art
In Transmission Control Protocol (TCP) networks, congestion appears in intermediate network nodes (e.g., routers) when data in-flow is higher than data out-flow. In these instances the load is temporarily higher than what the resources are able to process, leading to increased delays, throughput reduction, and packet loss (although packets may be retransmitted in the case of TCP).
Current attempts to resolve congestion problems in TCP networks include the use of congestion control algorithms (CCA). Congestion control algorithms may be divided into delay based approaches and loss based approaches. In delay based approaches, the CCA makes congestion decisions to reduce data transmission rates and adjust the transmission rates based on round trip time (RTT) variations. RTT is determined based on estimates and/or actual measurements of delay. However, with delay-based congestion control algorithms an inherent problem is that if the actual propagation delay is inaccurately estimated by baseRTT (i.e., the observed minimum RTT), an unfair share of the resources occurs and severe oscillation of router queues may occur. On the other hand, loss based approaches use packet loss as the only indication of congestion. Theoretical analysis and experiments show that delay-based approaches generally have better properties, such as utilization and RTT fairness, than loss-based approaches. Nevertheless, these approaches both suffer from serious shortcomings.